I ntroducon to MemSQL MemSQL supports indexing on Rowstore (Skiplist and Hash indexes) and Columnstore (Hash indexes) to efficiently retrieve rows as needed. Distributed Query Processing MemSQL supports fast distributed query processing, with a query opmizer that is fully aware of data distribuon, and a query execuon system that takes advantage of compilaon and vectorizaon , achieving 10X to 100X performance gains. The following diagram illustrates MemSQL query processing at a high level. Query Opmizaon The MemSQL Query Opmizer uses search and heuriscs, driven by cost models based on stascs, to find high-quality distributed query execuon plans. The opmizer is fully aware of data distribuon and can use broadcast, shuffle, local-global aggregaon, s emi-join reducon, and co-located join Figure8. Query opmizaon operaons to solve queries with limited and judicious use of data movement across the cluster. Stascs and summary informaon available to the opmizer include disnct count informaon, histograms, and high-quality random samples of data from both row store and column store tables. The MemSQL Query Opmizer is a modular component in the database engine. The opmizer framework is divided into three major modules: 13